程序可以正常输出，但有警告

Question

#include "stdio.h"
#include "stdlib.h"
#include "malloc.h"
#define MaxSize 100
typedef char ElemType;

typedef struct
{
    char data[MaxSize];
    int length;
} SqString;

void StrAssign(SqString &s, char cstr[])
{
    int i;
    for (i = 0; cstr[i] != '\0'; i++)
        s.data[i] = cstr[i];
    s.length = i;
}

void DestroyStr(SqString &s)
{
}

void StrCopy(SqString &s, SqString t)
{
    int i;
    for (i = 0; i < t.length; i++)
        s.data[i] = t.data[i];
    s.length = t.length;
}

bool StrEqual(SqString s, SqString t)
{
    bool same = true;
    int i;
    if (s.length != t.length)
        same = false;
    else
        for (i = 0; i < s.length; i++)
            if (s.data[i] != t.data[i])
            {
                same = false;
                break;
            }
    return same;
}

int StrLength(SqString s)
{
    return s.length;
}

SqString Contact(SqString s, SqString t)
{
    SqString str;
    int i;
    str.length = s.length + t.length;
    for (i = 0; i < s.length; i++)
        str.data[i] = s.data[i];
    for (i = 0; i < t.length; i++)
        str.data[s.length + i] = t.data[i];
    return str;
}

SqString SubStr(SqString s, int i, int j)
{
    int k;
    SqString str;
    str.length = 0;
    if (i <= 0 || i > s.length || j < 0 || i + j - 1 > s.length)
        return str;
    for (k = i - 1; k < i + j - 1; k++)
        str.data[k - i + 1] = s.data[k];
    str.length = j;
    return str;
}

SqString InsStr(SqString s1, int i, SqString s2)
{
    int j;
    SqString str;
    str.length = 0;
    if (i <= 0 || i > s1.length)
        return str;
    for (j = 0; j < i - 1; j++)
        str.data[j] = s1.data[j];
    for (j = 0; j < s2.length; j++)
        str.data[i + j - 1] = s2.data[j];
    for (j = i - 1; j < s1.length; j++)
        str.data[s2.length + j] = s1.data[j];
    str.length = s1.length + s2.length;
    return str;
}

SqString DelStr(SqString s, int i, int j)
{
    int k;
    SqString str;
    str.length = 0;
    if (i <= 0 || i > s.length || i + j > s.length + 1)
        return str;
    for (k = 0; k < i - 1; k++)
        str.data[k] = s.data[k];
    for (k = i + j - 1; k < s.length; k++)
        str.data[k - j] = s.data[k];
    str.length = s.length - j;
    return str;
}

SqString RepStr(SqString s, int i, int j, SqString t)
{
    int k;
    SqString str;
    str.length = 0;
    if (i <= 0 || i > s.length || i + j - 1 > s.length)
        return str;
    for (k = 0; k < i - 1; k++)
        str.data[k] = s.data[k];
    for (k = 0; k < t.length; k++)
        str.data[i + k - 1] = t.data[k];
    for (k = i + j - 1; k < s.length; k++)
        str.data[t.length + k - j] = s.data[k];
    str.length = s.length - j + t.length;
    return str;
}

void DisStr(SqString s)
{
    int i;
    if (s.length > 0)
    {
        for (i = 0; i < s.length; i++)
            printf("%c", s.data[i]);
        printf("\n");
    }
}

int main(int argc, char *argv[])
{
    SqString s, s1, s2, s3, s4;
    printf("顺序串的基本运算如下：\n");
    printf("(1)建立串s=\"abcdefghefghijklmn\"和串s1=\"xyz\"\n");
    StrAssign(s, "abcdefghefghijklmn");
    StrAssign(s1, "xyz");
    printf("(2)输出串s:");
    DisStr(s);
    printf("(3)输出串s的长度：%d\n", StrLength(s));
    printf("(4)在串s的第9个字符位置插入s1而产生串s2\n");
    s2 = InsStr(s, 9, s1);
    printf("(5)输出串s2：");
    DisStr(s2);
    printf("(6)删除串s的第2个字符开始的5个字符而产生串s2\n");
    s2 = DelStr(s, 2, 5);
    printf("(7)输出串s2：");
    DisStr(s2);
    printf("(8)将串s的第2个字符开始的5个字符替换成串s1而产生串s2\n");
    printf("(9)输出串s2：");
    s2 = RepStr(s, 2, 5, s1);
    DisStr(s2);
    printf("(10)提取串s的第2个字符开始的10个字符而产生串s3\n");
    s3 = SubStr(s, 2, 10);
    printf("(11)输出串s3：");
    DisStr(s3);
    printf("(12)将串s1和串s2连接起来而产生串s4\n");
    s4 = Contact(s1, s2);
    printf("(13)输出串s4：");
    DisStr(s4);
    return 0;
}

输出：
PS E:\vscode> cd "e:\vscode\C++" ; if ($?) { g++ 第6次实训.cpp -o 第6次实训 } ; if ($?) { .\第6次实训 }
第6次实训.cpp: In function 'int main(int, char**)':
第6次实训.cpp:144:38: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
StrAssign(s, "abcdefghefghijklmn");
^
第6次实训作业.cpp:145:24: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
StrAssign(s1, "xyz");
^
顺序串的基本运算如下：
(1)建立串s="abcdefghefghijklmn"和串s1="xyz"
(2)输出串s:abcdefghefghijklmn
(3)输出串s的长度：18
(4)在串s的第9个字符位置插入s1而产生串s2
(5)输出串s2：abcdefghxyzefghijklmn
(6)删除串s的第2个字符开始的5个字符而产生串s2
(7)输出串s2：aghefghijklmn
(8)将串s的第2个字符开始的5个字符替换成串s1而产生串s2
(9)输出串s2：axyzghefghijklmn
(10)提取串s的第2个字符开始的10个字符而产生串s3
(11)输出串s3：bcdefghefg
(12)将串s1和串s2连接起来而产生串s4
(11)输出串s4：xyzaxyzghefghijklmn